1. Field of the Invention
This invention relates to composite parts comprising sprayed polyurethaneureas and to a process for their production.
2. Description of Related Art
Composite articles and processes for preparing composite articles are known and described in various references. Composite articles which may be fiber-reinforced and have an aesthetic visual surface are suitable for use as pleasure craft hulls, personal watercraft, sea plane pontoons, hot tubs, bathtubs, swimming pools and other items used in aqueous environments. A multi-step process is known for making various watercraft hulls and fiberglass reinforced articles. Polyurethanes and polyureas have been used to make structural supports, composite articles and sandwich structures for a number of years.
Polyurethane and polyurea composites and processes for the production of these composites is described in, for example, U.S. Pat. Nos. 5,192,594, 5,233,009, and 5,275,888, and U.S. Published Patent Application 2005/0075450.
U.S. Pat. No. 5,192,584 discloses a process of preparing polyurethaneurea structural supports in which a polyurethane is sprayed onto a substrate. The polyurethane is the reaction product of a specific polyol blend, an organic diamine and an isocyanate component, in the presence of a moisture absorbing material and a polysiloxane defoaming agent. These polyurethanes can be spray applied to a substrate.
A process for the preparation of composite structures comprising a ceramic layer and polyurethane layers and the polyurethane compositions used in this process are disclosed in U.S. Pat. Nos. 5,233,009 and 5,275,888. These composites are suitable for use in plumbing applications including bathtubs. The polyurethanes comprise a specific polyol blend, an organic diamine, fillers and an isocyanate-terminated prepolymer. Composite structures can be prepared by spray applying these polyurethanes to an adhesive coated ceramic enamel layer.
Fiber reinforced composites prepared from a polyurethane system are described in U.S. Published Patent Application 2005/0075450. These polyurethanes comprise a highly hydrophobic polyol component with an isocyanate prepolymer, in which the combination has a combined functionality of greater than 5. These systems are suitable as gel coats and matrix resins, and produce little to no volatile emissions. Boat hulls and other similar products can be produced from these systems.
Polyurethane sandwich structure elements and a process for the production of these are disclosed in U.S. Pat. No. 5,856,371. These sandwich structures are self-supporting and comprise at least one non-cellular polyurethane layer and at least one polyurethane foamed layer, with the non-cellular layer containing 10 to 55% by weight of mica. The mixtures used to form each polyurethane layer contain a polyether polyol having an OH number of 250 to 400, a semi-prepolymer based on diphenylmethane diisocyanate and a polyether polyol and which have an NCO group content of 20 to 30%, and optionally, foaming agents, with the mixtures being reacted at an isocyanate index of 90 to 130.
U.S. Pat. No. 5,104,693 discloses polyurethane backed substrates such as carpet cushions. The polyurethane foaming composition comprises a soft segment prepolymer of diphenylmethane diisocyanate or a derivate thereof, an isocyanate-reactive mixture having an average equivalent weight of 1000 to 5000, and an effective amount of a blowing agent.
Advantages of the present invention include ease in processing, lower reaction exotherm, and most importantly, better impact resistance in the resulting PUR composite. Ease in processing is accomplished by utilizing a prepolymer so that the viscosity of it and the polyol blend coreactant are more equal than in systems using unmodified polyisocyanates. This eases mixing of the two components but also may make it possible to utilize more convenient mix ratios by volume (e.g. 1:1 and 1:2). Utilizing prepolymers also limits the amount of heat which evolves in the curing reaction so that heat sensitive substrates (e.g. thermoplastic shells or gel coats) are less affected. Most importantly, the impact resistance of the PUR is improved compared to that of systems that do not contain soft segments or one that contain these soft segments solely in the coreactant portion (i.e. non-isocyanate portion) of the PUR system.